Data Mining in a Digital Map Database to Identify Decreasing Radius of Curvature Along Roads and Enabling Precautionary Actions in a Vehicle

ABSTRACT

Disclosed is a feature for a vehicle that enables taking precautionary actions in response to conditions on the road network around or ahead of the vehicle, in particular, a curved portion of a road where the curvature increases between adjacent curved sections. A database that represents the road network is used to determine locations where curvature between adjacent curved sections increases. Then, precautionary action data is added to the database to indicate a location at which a precautionary action is to be taken about the location where curvature increases. A precautionary action system installed in a vehicle uses this database, or a database derived therefrom, in combination with a positioning system to determine when the vehicle is at a location that corresponds to the location of a precautionary action. When the vehicle is at such a location, a precautionary action is taken by a vehicle system as the vehicle is approaching a location where the curvature increases.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 37 C.F.R. §1.53(b) of U.S.patent application Ser. No. 12/156,224 filed May 30 2008 (AttorneyDocket No. 10171/12035AUS (NC58200US)) now U.S. Pat. No. ______, theentire disclosure of which is hereby incorporated by reference. Thepresent patent application is related to patent application Ser. No.12/156,264, filed on May 30, 2008, now U.S. Pat. No. ______, entitled“DATA MINING TO IDENTIFY LOCATIONS OF POTENTIALLY HAZARDOUS CONDITIONSFOR VEHICLE OPERATION AND USE THEREOF,” Attorney Docket No. NO260US, theentire disclosure of which is incorporated by reference herein.

BACKGROUND

The present invention relates to a method and system that enables takinga precautionary action in a vehicle, such as providing a warning to avehicle driver about a potentially difficult or hazardous drivingcondition on the road network.

Advanced driver assistance systems (“ADAS”), including active safety andfuel economy systems, have been developed to improve the comfort,efficiency, safety, and overall satisfaction of driving. Examples ofthese advanced driver assistance systems include adaptive headlightaiming, adaptive cruise control, lane departure warning and control,curve warning, speed limit notification, hazard warning, predictivecruise control, and adaptive shift control, as well as others. Some ofthese advanced driver assistance systems use a variety of sensormechanisms in the vehicle to determine the current state of the vehicleand the current state of the roadway in front of the vehicle. Thesesensor mechanisms may include radar, infrared, ultrasonic andvision-oriented sensors, such as digital video cameras and lidar. Someadvanced driver assistance systems also use digital map data. Digitalmap data can be used in advanced driver assistance systems to provideinformation about the road network, road geometry, road conditions andother items associated with the road and terrain around the vehicle.Digital map data is not affected by environmental conditions, such asfog, rain or snow. In addition, digital map data can provide usefulinformation that cannot reliably be provided by cameras or radar, suchas curvature, grade, bank, speed limits that are not indicated bysignage, traffic and lane restrictions, etc. Further, digital map datacan provide a predictive capability well beyond the range of othersensors or even beyond the driver's vision to determine the road aheadof the vehicle, around corners, over hills or beyond obstructions.Accordingly, digital map data can be a useful addition for some advanceddriver assistance systems.

Although these kinds of systems provide useful features, there existsroom for further improvements. For example, it would be useful toidentify locations on the road network where a relatively high number oftraffic accidents have occurred. However, statistics pertaining toaccidents are maintained by various different administrative entitiesthat use different formats, standards, reporting methods, reportingperiods, etc. Accordingly, it is difficult to obtain consistentinformation about traffic accidents on roads in a large geographicregion, such as the entire United States or Europe. Moreover, dataindicating locations where a statistically large number of trafficaccidents occur may not indicate the causes of the accidents or howaccidents can be avoided.

Accordingly, it is an objective to provide a system that facilitatestaking a precautionary action in a vehicle, such as providing a warningto a vehicle operator, when approaching a location where accidents mayoccur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of a portion of a road network with a curvewith a decreasing radius of curvature.

FIG. 1B is an illustration of how the portion of a road network shown inFIG. 1A is represented as data in a database.

FIG. 2 is a flowchart of a process that uses a database that representsa road network to identify conditions such as the one shown in FIG. 1.

FIG. 3 is a diagram of a data record formed by the process of FIG. 2.

FIG. 4 is a diagram of a vehicle system that uses data produced by theprocess of FIG. 2.

FIG. 5 is a flowchart of a process performed by the system of FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED EMBODIMENTS

To address these and other objectives, the present invention comprises afeature that enables taking a precautionary action in a vehicle as thevehicle approaches the location of a curve that has a decreasing radiusof curvature. The precautionary action may be a warning message providedto the vehicle driver to alert the vehicle driver about the curve withthe decreasing radius of curvature so that the vehicle driver can payextra attention. Alternatively, the precautionary action may be anactual modification of the operation or control of the vehicle, such asbraking, accelerating, or maneuvering the vehicle, or activating asensor. Alternatively, the precautionary action may be providing aninput to an algorithm that also processes inputs from other sensors fortaking such actions. In another alternative, the precautionary actionmay include a combination of any of these aforementioned actions.

According to another aspect, a database that represents the road networkis used to determine locations where there are curves with decreasingradii of curvature. Then, precautionary action data is added to thedatabase to indicate each location at which a precautionary action is tobe provided about a curve with a decreasing radius of curvature.

According to further aspects, a precautionary action system installed ina vehicle uses this database, or a database derived therefrom, incombination with a positioning system, to determine when the vehicle isat a location that corresponds to the location where a precautionaryaction should be taken. When the vehicle is at such a location, theprecautionary action is taken, such as providing a warning to thevehicle operator, as the vehicle is approaching a curve with adecreasing radius of curvature. Alternatively, the precautionary actionmay consist of an actual modification of the operation or control of thevehicle, such as braking, accelerating, or maneuvering the vehicle, oractivating a sensor. Alternatively, the precautionary action may includeproviding an input to an algorithm that also processes inputs from othersensors for taking such actions. Alternatively, the precautionary actionmay be an adjustment of sensitivities of other ADAS applications such asincreasing the control authority and sensitivity of a lane departurewarning or control system to lane edge approach and violation. Inanother alternative, the precautionary action may include a combinationof any of these aforementioned actions.

FIG. 1A depicts road segments 10, 12 and 14. The road segments 10, 12and 14 meet at an intersection 16. As shown in FIG. 1A, the road segment10 is curved. The degree by which a road segment curves is described byits curvature. There are various ways to indicate or measure curvature.Curvature refers to a property of a road segment and is an indication ofhow much the road is curved. As shown in FIG. 1A, the road segment 10starts out with a straight portion 18, followed by a portion 20 that ismoderately curved, which is followed a portion 22 that is more curved.

FIG. 1B is an illustration of how the road segments in FIG. 1A arerepresented by data contained in a map database (such as the database110 in FIG. 2). The road segments are each represented by a data recordthat defines a line that extends between two endpoints, or nodes. Thelocation of the road segment is defined by the data indicating thelocations (e.g., geographic coordinates, including altitude) of thenodes. As shown in FIG. 1B, the road segment 10 is represented by theline 28, the road segment 12 is represented by the line 30, and the roadsegment 14 is represented by the line 32.

The data record that represents each road segment includes data thatindicates the shape of the road segment. One way to represent the shapeof the road segment is to define shape points along the road segment.Shape points indicate the geographic coordinates at points along theroad segment between the nodes. In the case of a straight road segment,no shape points are required. However, in the case of a curved roadsegment, one or more shape points are used to define locations along theroad segment. FIG. 1B shows several shape points, 34, 36, 38 . . . 48,defined along the road segment between the endpoints, i.e., nodes 50 and52. Thus, the curved road segment 10 in FIG. 1A is represented by anapproximation 28 comprised of a series of short, straight lines as shownin FIG. 1B. (Alternatively, a database may represent a curved roadsegment by a curved line, such as a spline, clothoid, etc. In thisalternative, data that defines the curved line is included in thedatabase.) As indicated in FIG. 1B, in the first portion 54 of the line28, which corresponds to the straight portion 20 of road segment 10 inFIG. 1A, there are no shape points. In the portion 56 of the line 28,which corresponds to the curved portion 22 of the road segment 10 inFIG. 1A, there are a series of shape points, 34, 36 and 38. In theportion 58 of the line 28, which corresponds to the more curved portion24 of the road segment 10 in FIG. 1A, there are a series of shapepoints, 40, 42, 44, 46 and 48, which are more closely spaced togetherthan those in portion 56.

FIG. 2 is a flowchart of a process 100. The process 100 is performed bya software program or routine that is run on a suitable computingplatform, such as a database server, PC or plurality of PCs coupledtogether for parallel computing applications.

The process 100 uses a database 110 that contains data that representsthe road network in a region. The region may be a country, such as theUnited States, Germany, France or Korea. Alternatively, the region mayinclude several countries or an entire continent. According to anotheralternative, the region may include only a portion of a country, such asa state or several states or metropolitan areas.

The process 100 is performed by a map developer, such as NAVTEQCorporation. Alternatively, the process 100 may be performed by anotherentity that has access to an editable version of a map database 110. Forexample, the process may be performed by a customer or licensee ofNAVTEQ, such as a manufacturer of navigation systems or active safetysystems, or by a traffic information services company or by a governmentoffice at any level.

The database 110 is in a format that can be edited. That is, new orupdated information can be added to the database 110. Alternatively, thedatabase 110 is in a format such that new information can be combinedwith the original data to form a new database that includes both theoriginal data and new data. In one embodiment, the database is in anOracle spatial format. Alternatively, the database may be in deliveryformat, such as GDF (Geographic Data File), SIF (Standard InterchangeFormat), or other formats, including proprietary formats.

As stated above, the database 110 contains data that represents the roadnetwork in the region. The database 110 contains information such as thelocations (geographic coordinates, including altitude) of roads andintersections, road names, the three-dimensional shape of the roadsincluding curvature, slope and bank, speed limits along roads, turnrestrictions at intersections, addresses or address ranges along roads,the number of lanes each road has, lane width, lane markings, functionalclasses of roads, the locations of medians, and so on. The database mayalso contain information about other geographic features, such as bodiesof water, parks, administrative areas (including municipal, state andcountry boundaries), and locations of points of interest, such asbusinesses, hospitals, police stations, and so on.

In FIG. 2, the process 100 examines each data record that represents aroad segment (also referred to herein as a “link”) to determine whetherit represents one similar to the road segment 10 in FIG. 1A. (Theprocess 100 may use a procedure that examines in turn each data recordthat represents each road segment represented in the entire database.)In one step, a data record that represents a link or road segment isread from the database 110 (Step 130). This road segment record mayinclude data (e.g., shape points) that indicate whether the road segmentis curved. This data is evaluated (Step 134). If the represented roadsegment is not curved, the process 100 proceeds to a step in which it isdetermined whether all the road segment records in the database havebeen examined (Steps 136 and 138). If there are more segment records toexamine, the process 100 proceeds to get the next segment record (Step130) and continues.

Referring back to Step 136, if the represented road segment is curved,the process 100 proceeds to evaluate the data that indicates thecurvature along the road segment's curved portion to determine whetherthe curvature changes, i.e., increases, in a given direction (Step 144).More specifically, the process evaluates the curvature to determine ifcurvature is approximately constant for a given length, and thenincreases in curvature to a higher value for another length. The processmay use a threshold by which the curvature is required to increase todetermine that the condition is met. The process may use the spacingbetween shape points to determine whether the curvature increases alongthe length of a road segment. From an evaluation of the degree ofcurvature, as well as the amount by which the curvature changes, it isdetermined whether there exists a sufficiently large change in curvatureto constitute a potentially hazardous condition (such as the change incurvature between the sections 22 and 24 shown in FIG. 1A). Ifexamination of the segment's curvature indicates that there is not asufficiently large change in curvature between adjacent portions of theroad, the process 100 proceeds to the step in which it is determinedwhether all the road segment records in the database have been examined(Step 138) and if there are more segment records to examine, the process100 proceeds to get the next segment record (Step 130).

Referring back to Step 150, if examination of the segment's curvaturebetween adjacent sections indicates that there is a sufficiently largechange between sections, the process 100 adds precautionary action data160 to the database 110 (Step 156). The precautionary action data 160indicates the presence of a feature in the road network where aprecautionary action may be taken.

After the precautionary action data 160 is added to the database 110,the process 100 proceeds to the step in which it is determined whetherall the road segment records in the database have been examined (Step138) and if there are more segment records to examine, the process 100proceeds to get the next segment record (Step 130).

The process 100 ends when it is determined whether all the road segmentrecords have been examined (Step 138).

It is noted that the process 100, above, performs a data miningfunction. The existence of the potentially difficult location, i.e., asignificant increase in curvature between adjacent road sections along acurve, is derived from data already collected and present in thedatabase. It is noted that the process 100, above, evaluates multipledata items in the original database, to determine whether the conditionexists, in this case, adjacent road sections in which the curvatureincreases by a significant amount. By evaluating these multiple dataitems, a determination is made whether these multiple data itemsdescribe the condition of interest. If these data items do describe thecondition, a new data item, i.e., the precautionary action data, isadded to the database.

The above process for determining whether a sufficiently large increasein curvature exists between adjacent road sections can take into accountother factors, such as speed limits, road surface, the presence and typeof shoulders, and so on. According to this alternative, the thresholdmay take into account the speed limit along the road segment (which isalso stored as data in the database 110.)

FIG. 3 is a diagram that shows a data record 200 in the database 110.The data record 200 represents a road segment located in a geographicregion. As explained above, the geographic region may include an entirecountry or continent. Accordingly, the database 110 includes many datarecords like the one shown in FIG. 3.

The data record 200 shown in FIG. 3 is exemplary and shows only one wayto represent a road segment. Databases may represent road segments invarious different ways and may include different kinds of information.The present invention is not limited to any particular way ofrepresenting roads.

Referring to FIG. 3, various data are associated with the data record200 that represents a road segment. This various data indicates featuresor attributes of the represented road segment. For example, associatedwith the data record is data that indicates the permitted direction(s)of travel. Also associated with the road segment record 200 are datathat indicate a speed limit, a classification of the road segment (i.e.,the type of road, such as controlled access, etc.), a rank (e.g., 1-4),the endpoints of the road segment, shape points (i.e., locations alongthe road segment between its endpoints). Also associated with the roadsegment records is data that indicate the successors at each endpoint.Successors are those road segments that connect to the represented roadsegment at each of its endpoints. The segment record 200 may identifythese successors by reference to the data records that represent thesuccessors.

In FIG. 3, the database 110 also includes precautionary action data 160.The precautionary action data 160 is the data added to the database 110by the process 100 in FIG. 2. In FIG. 3, the precautionary action data160 is shown as added to the road segment record 200. It should beunderstood that the process 100 adds precautionary action data 160 withrespect to only certain records, i.e., records that represent thoseroads segments that meet the conditions identified by the process.Accordingly, the database 110 will contain data records that representroad segments that contain the precautionary action data 160 and otherdata records that represent road segments that do not contain theprecautionary action data 160.

In the embodiment shown in FIG. 3, the precautionary action data 160 isassociated with the road segment identified as having a significantincrease in curvature between adjacent road sections along a curve. Inthis embodiment, the precautionary action data 160 includes severalcomponents. One component 160(1) indicates a condition type. Thiscondition type 160(1) indicates the type of condition about which aprecautionary action is to be taken, which in this case is a significantincrease in curvature between adjacent road sections along a curve. Thiscondition type 160(1) component is used when different conditions areidentified in the database 110 about which precautionary action may betaken.

Another component of the precautionary action data 160 is theprecautionary action location 160(2). The precautionary action location160(2) indicates where along the represented road segment aprecautionary action may be taken. The precautionary action location160(2) data may include multiple entries. For example, the precautionaryaction location 160(2) may indicate where a warning may be provided to avehicle driver to advise the driver about the upcoming condition, i.e.,the significant increase in curvature between adjacent road sectionsalong a curve. In the case of a significant increase in curvaturebetween adjacent road sections along a curve, the warning location160(2) may indicate a distance (e.g., x meters) from the changingcurvature. The location 160(2) is determined based on an analysis offactors, such as the superelevation, curvature, the change of curvature,the speed limit along the represented road segment, the roadclassification, and possibly other factors. These factors may bedetermined from other data contained in the database 110. According toone example, the location 160(2) may indicate that a warning should beprovided at a location 400 meters along the road segment from the curve.

The precautionary action location 160(2) may also indicate where avehicle control action should be taken, such as tightening theseatbelts, pre-loading or engaging the brakes, tightening sensitivitiesof lane departure warning systems or stability control systems, etc.This may be a different location from where the precautionary warning isprovided and would be based on a different analysis of factors.

Another component of the precautionary action data 160 is direction data160(3). The direction data 160(3) indicates the direction along therepresented road segment where the precautionary action should be taken.In this case, the direction data 160(3) would indicate the direction inwhich the curvature increases as one travels along the road. (Note thatthe database 110 may indicate a direction along a road segment aspositive or negative based on the relative latitude and longitude of theroad segment endpoints.)

Another component of the precautionary action data 160 is a reference160(4). In this case, the reference 160(4) indicates the location of thesignificant increase in curvature between adjacent road sections along acurve. The reference 160(4) refers to shape points that represent thecurved portions of the road.

The precautionary action data 160 described in FIG. 3 is one way thatthis data may be included in a database that represents a geographicregion. There are alternative ways to include the precautionary actiondata. For example, the precautionary action data may be included asseparate data records in the database 110. If included as separate datarecords, the precautionary action data may be associated with the roadsegments to which they apply by pointers or other suitable datareferences. Alternatively, the precautionary action data may beassociated with node data records, instead of the road segments leadingto the intersections. Various other ways exist and the present inventionis not intended to be restricted to any specific implementation.

FIG. 4 is a diagram depicting components of a vehicle 300. The vehicle300 is operated on a road network, such as the road network representedby the database 110 in FIG. 2. The vehicle 300 may be an automobile,truck, bicycle, motorcycle, etc.

The vehicle 300 includes systems 310. In this embodiment, the vehiclesystems 310 include a positioning system 320. The positioning system 320determines the position of the vehicle 300 on the road network. Thepositioning system 320 includes appropriate hardware and software todetermine the position of the vehicle 300. For example, the positioningsystem may include hardware 322 that includes a GPS unit, anaccelerometer, wheel speed sensors, etc. The positioning system 320 alsoincludes a positioning application 324. The positioning application 324is a software application that uses outputs from the positioning systemhardware 322 and information from a map database 330. The positioningapplication 324 determines the position of the vehicle 300 with respectto the road network, including the location of the vehicle 300 along aroad segment and a direction of travel of the vehicle along the roadsegment.

In one embodiment, the map database 330 is located in the vehicle. In analternative embodiment, the map database 330 may be located remotely andaccessed by the vehicle systems 310 using a wireless communicationsystem. In yet another embodiment, part of the map database 330 may belocated locally in the vehicle and part of the map database 330 may belocated remotely.

The map database 330 is stored on a computer readable medium 334. Thecomputer-readable medium may be implemented using any suitabletechnology. For example, the computer readable medium may be a DVD disk,a CD-ROM disk, a hard disk, flash memory, or any other medium, or aplurality of media.

The map database 330 includes data that represents the geographic regionin which the vehicle 300 is being operated. The map database 330 mayrepresent the same geographic region as the database 110 in FIG. 2, oralternatively, the map database 330 may represent only a portion of theregion represented by the database 110.

The map database 330 used by the vehicle systems 310 may be in adifferent format from the database 110 in FIG. 2. The map database 330is formed or derived from the database 110 by a compilation process thatorganizes and presents the data in a form and format that specificallyfacilitates its use for performing specific functions. For example, themap database 330 may be separated into different collections of datathat are used for specific functions, such as vehicle positioning, routecalculation, map display, route guidance, destination selection, and soon. The map database 330 may also be organized into groupings spatially.One kind of compiled database format is disclosed in U.S. Pat. No.5,968,109, the entire disclosure of which is incorporated by referenceherein. Various other compiled database formats exist, includingproprietary formats, and the disclosed embodiment(s) are not limited toany particular format.

Included among the vehicle systems 310 in FIG. 4 is a navigation system340. The navigation system 340 uses outputs from the positioning system320 and data from the map database 330 to provide navigation-relatedfeatures to a vehicle user, e.g., the vehicle operator or passenger. Thenavigation system 340 includes applications for route calculation 344,map display 346, as well as possibly other applications. The navigationsystem 340 provides the navigation-related features to the vehicle uservia a user interface 354. (The navigation system 340 is optional and maybe omitted.)

Also included among the vehicle systems 310 is a precautionary actionapplication 350. The precautionary action application 350 uses outputsfrom the positioning system 320 and data from the map database 330 totake precautionary actions, such as provide warnings to the vehicleoperator. The precautionary action application 350 provides the warningto the vehicle operator via the user interface 354.

FIG. 4 also shows that precautionary action application 350 provides anoutput to vehicle control systems and actuator 356. The vehicle controlsystems and actuator are operatively connected to various vehiclemechanical systems, such as the vehicle's brakes 356(1), engine 356(2),seatbelts (including tensioners) 356(3), airbags 356(4), stabilitycontrol algorithms, as well as other system systems 356(5).

FIG. 5 is a flowchart 400 showing operation of the precautionary actionapplication 350 (in FIG. 4). As the vehicle 300 (in FIG. 4) is beingoperated on a road, the precautionary action application 350 obtains thecurrent vehicle position from the positioning system 320 (Step 410).(During vehicle operation, the positioning system 320 continuouslydetermines the current geographic position of the vehicle 300 as thevehicle is being operated using data from the map database 330.) Thepositioning system 320 provides the precautionary action applicationwith data that indicates the current vehicle position with respect tothe road network as represented by the map database 330. Specifically,the location of the vehicle along a road segment and the direction oftravel of the vehicle along the road segment are determined and providedto the precautionary action application 350.

Next, the process 400 obtains data from the map database 300 thatrepresents the geographic features (i.e., roads, intersections, etc.) atthe current location of the vehicle and in the direction in which thevehicle is heading (Step 420). In one embodiment, an electronic horizonis used (Step 430). Building an electronic horizon and using it toprovide warnings are disclosed in U.S. Pat. Nos. 6,405,128 and 6,735,515and U.S. patent application Ser. No. 11/400,151, the entire disclosuresof which are incorporated by reference herein. Using an electronichorizon and/or the inventions disclosed in these patents and pendingpatent application is optional and the disclosed process 400 is notlimited to using the electronic horizon technology.

After obtaining data from the map database 300 that represents thegeographic features at the current location of the vehicle and in thedirection in which the vehicle is heading, the process 400 includes thestep of examining the data to determine whether any precautionary actiondata (160 in FIG. 3) is associated with the represented geographicfeatures (Step 440). If there is no precautionary action data associatedwith the represented geographic features, the process 400 loops back toget a new current vehicle position (Step 410). On the other hand, ifthere is precautionary action data associated with the representedgeographic features, the process 400 takes a precautionary action (Step450). The precautionary action may be a warning provided to the vehicleoperator when the vehicle is at the location (i.e., 160(2) in FIG. 3)indicated by the precautionary action data. The warning may be providedvia the user interface 354. The warning may be an audible warningmessage or a visual warning.

The precautionary action is not limited to warnings, but may alsoinclude other actions. For example, in the case of a significantincrease in curvature between adjacent road sections along a curve,vehicle systems 356, such as the brakes, engine or transmission, can bereadied for a deceleration. In addition, the seatbelts may be tightenedor the airbags set to deploy. As explained above, to facilitate thesekinds of actions, additional information may be added to the warningdata 160 (in FIG. 3) to indicate the type of action as well as thelocation where the action should be taken.

Referring still to FIG. 5, after taking the precautionary action, theprocess 400 loops back to get a new current vehicle position (Step 410).

Alternative with Dynamic Data

The process (400 in FIG. 5) was described as a way to use theprecautionary action data that had been stored in the map database totake an appropriate action in a vehicle when the vehicle is at or isapproaching a location identified as having a potentially hazardouscondition. This process uses a positioning system and map database inthe vehicle to determine when the vehicle is at or is approaching such alocation. The process may also take into account dynamic information.Dynamic information may include current traffic and weather conditions,ambient light conditions, road conditions (e.g., ice), and so on. Thevehicle may include systems to obtain such information. For example, thevehicle may have a traffic data receiver that obtains real-time trafficinformation, e.g., RDS-TMC messages. The process 400 may use the dynamicinformation in combination with the precautionary action data. Forexample, the process may modify the location at which a warning isprovided. As an example, if weather conditions indicate that it israining, the location at which a warning is provided to the vehicledriver about an upcoming curve with a significant increase in curvaturebetween adjacent road sections along a curve may be modified, i.e.,adjusted to a point farther in advance of the location of the hazardouscondition, in order to give the vehicle operator additional time ordistance. The process may even take certain actions only under certainconditions. For example, a warning about a significant increase incurvature between adjacent road sections along a curve may be providedonly during nighttime hours or during inclement weather conditions.

Verification

The process (100 in FIG. 2) was described as a way to automaticallyexamine records in a database that represents roads to identifylocations or conditions along the road network where a precautionaryaction might be taken. According to the described process, data is thenadded to indicate the location where the precautionary action should betaken. Alternatively, instead of automatically adding the precautionaryaction data to the database, the locations where such conditions areidentified could be marked on a temporary basis. Then, a geographicanalyst (or other human operator) could review some or all suchtemporarily marked locations. The analyst may conduct this review byphysically traveling to the locations or by reviewing satellite oraerial photographs of the locations, or video taken while driving by thelocations (previously or subsequently acquired either by the analyst orothers including members of the public). Based on the review, theanalyst then determines whether precautionary action data should beadded to the database.

It is intended that the foregoing detailed description be regarded asillustrative rather than limiting and that it is understood that thefollowing claims including all equivalents are intended to define thescope of the invention.

I claim:
 1. A method for augmenting a database that represents a roadnetwork in a geographic region, the method comprising: prior toinstallation of the database in a vehicle navigation system: using datacontained in the database to identify road segments of the road networkhaving a non-constant curvature which increases in one direction oftravel and, for each identified road segment, adding precautionaryaction data to the database associated with the data recordrepresentative of the identified road segment to indicate the presenceof a condition for which a precautionary action is to be taken when avehicle approaches the associated road segment in the direction oftravel in which the curvature increases; and wherein the vehiclenavigation system is configured to indicate that a precautionary actionshould be taken when the vehicle approaches a road segment representedin the database by a data record associated with precautionary actiondata.
 2. The method of claim 1 wherein the using further comprisesevaluating curvature of each road segment of the road network todetermine if the curvature is approximately constant for a first lengththereof, and then increases in curvature to a higher value for a secondlength succeeding the first length.
 3. The method of claim 2 furthercomprising comparing the increased curvature against a threshold bywhich the curvature is required to increase.
 4. The method of claim 2wherein the evaluating further comprises using spacing between shapepoints of the road segment to determine whether the curvature increasesalong the length thereof.
 5. The method of claim 2 wherein theevaluating further comprises determining the amount by which thecurvature changes from the first length to the second length.
 6. Themethod of claim 1 wherein the adding further comprises considering aspeed limit, road surface and/or a presence or type of shoulders of theroad segment when adding precautionary action data to the database. 7.The method of claim 1 wherein the precautionary action data furthercomprises data indicative of a distance to the increased curvature ofthe road segment.
 8. The method of claim 7 wherein the distance isdetermined based on an analysis of superelevation of the road segment,curvature of the road segment, the change of curvature of the roadsegment, the speed limit along the road segment, the road classificationof the road segment, or combinations thereof.
 9. The method of claim 1wherein the using further comprises: selecting from the database a datarecord that represents each of the road segments and determining whetheror not the road segment is curved; and upon determining that the roadsegment is curved, obtaining data that represents curvature values ofsections of the road segment.
 10. The method of claim 1 furthercomprising: continuing to select from the database data records thatrepresent road segments to identify all locations of curved roadsthroughout the geographic region where the curvature changes betweenadjacent sections.
 11. A database stored on a non-transitorycomputer-readable medium, wherein the database includes data thatrepresents a road network in a geographic region, wherein the databasecomprises: data records that represent road segments that make up theroad network; data that indicates curvature of each of the roadsegments; and data that indicates precautionary action locations,wherein a precautionary action location is associated with a location atwhich the data indicative of the curvature of a road segment furtherindicates that the curvature increases in one direction of travelthereof, wherein the data that indicates a precautionary action locationis operative to cause a vehicle navigation system to indicate that aprecautionary action should be taken when the vehicle approaches alocation associated therewith in the database in the direction of travelin which curvature increases.
 12. The database of claim 11 wherein theprecautionary action data further includes data that indicates alocation along a road segment at which a precautionary action is to betaken by a vehicle system.
 13. The database of claim 11 wherein theprecautionary action data further includes data that indicates adirection along a road segment at which a precautionary action is to betaken.
 14. The database of claim 11 wherein the precautionary actiondata further includes data that refers to the location of the actualincrease in curvature along the road.
 15. The database of claim 11further comprising data that indicates permitted directions of travelalong road segments, speed limits along road segments, classificationsof road segments, and locations of road segments.
 16. A vehicle systemcomprising: a database stored on a non-transitory computer-readablemedium, wherein the database includes data that represents a roadnetwork in a geographic region, wherein the database comprises: datarecords that represent road segments that make up the road network; datathat indicates curvature of each of the road segments; and data thatindicates precautionary action locations, wherein a precautionary actionlocation is associated with a location at which the data indicative ofthe curvature of each of the road segments further indicates that thecurvature increases in one direction of travel thereof; a positioningsystem that determines a current location of the vehicle relative to thedata representing a geographic region; and a precautionary actionapplication, responsive to the positioning system and the database, thatprovides a precautionary action when the positioning system determinesthat the vehicle is approaching a location associated with dataindicative of a precautionary action location in the direction of travelin which the curvature increases.
 17. The system of claim 16 wherein theprecautionary action data further includes data that indicates alocation along a road segment at which a precautionary action is to betaken by a vehicle system.
 18. The system of claim 16 wherein theprecautionary action data further includes data that refers to thelocation of the actual location of where the curvature increases.
 19. Amethod for providing precautionary actions in a vehicle comprising:determining a current position of the vehicle; accessing a database thatrepresents a road network to obtain data representations of a part ofthe road network around the current position of the vehicle, wherein thedatabase is stored on a non-transitory computer-readable medium, whereinthe database includes data that represents the road network in ageographic region, wherein the database comprises: data records thatrepresent road segments that make up the road network; data thatindicates curvature of each of the road segments; and data thatindicates precautionary action locations, wherein a precautionary actionlocation is associated with a location at which the data indicative ofthe curvature of each of the road segments further indicates that thecurvature increases in one direction of travel thereof; and upondetermining that the data representations of the part of the roadnetwork around the current position of the vehicle includesprecautionary action data indicating that an upcoming road segment hascurvature which increases in the direction of travel, taking aprecautionary action as the vehicle is at least approaching the upcomingroad segment.
 20. The method of claim 19 further comprising: building anelectronic horizon after accessing the database; and using theelectronic horizon to determine whether precautionary action data isincluded therein.
 21. The method of claim 19 wherein the precautionaryaction is provided via a user interface of the vehicle.